Rotary compressor-expander having spring biased vanes

ABSTRACT

A rotary unitary compressor-expander for use as a refrigeration device. The unit includes a stator defining a chamber having an oval cross-section and a rotor mounted within the chamber. The rotor contains a plurality of radial vane slots into each of which is inserted a vane which is radially slidable within its slot. Each vane includes, at either edge, a vane pin or stubshaft on which is rotatably mounted a vane roller. Oval cam tracks are provided at the ends of the stator chamber for engaging the vane rollers. One or more continuous spring bands are contained within the rotor and produce on the vanes an outwardly biasing force which urges the vane rollers into continuous contact with the cam tracks. The cam tracks are so symmectrically sized and positioned with respect to the stator chamber that with the vane rollers thus maintained in contact with the cam tracks, the vane tips are maintained in &#39;&#39;&#39;&#39;clearance&#39;&#39;&#39;&#39; sealing engagement with the wall of the stator chamber.

United States Patent Edwards et al. 1 1 Sept. 9, I975 [54] ROTARYC()MPRESS()R-EXPANDER 3,lH( 347 6/1965 Eickmantt 4|i'l/l52 SPRIN(;3,239,649 12/1960 Lamm 4 4lX/i78 [75] inventors: Thomas C. Edwards,Casselherry, FOREIGN PATENTS OR APPLICATIONS Fla; Claude Edwards,Espanola, N. 236,092 6/1945 Switzerland. .1 41H/13 Mex. 888,477 9/1943France 418/264 [73] Asslgneez Rovae Lurporatlon, Milliiilllti primaryb.'\luml.mlr juhn J. vmhlik Allurm'v, Agent, or l-'irmWolfe, Hubbard, Ledi y i: [22] Filed: Sept. 26, I973 Voit & Osann, Ltd

21 A I, N 400,965 I 1 Pp 157 ABSTRACT Relamd Apphcamm A rotary unitarycompressor-expander for use as a rel cmllinulliifln-i"-1141rtfrigeration device The unit includes a stator defining a chamber havingan oval cross'section and a rotor mounted within the chamber. The rotorcontains a [52] Hg/8i Hg/l3; 418/152; plurality of radial vane slotsinto each of which is in 8/258? Hg/9U? (x/263i serted a vane which isradially slidahle within its slot. V 413/294; 1 Each vane includes, ateither edge, a vane pin or stuh- Int 1/00; HVK 17m; 21/0; shaft on whichis rotatahly mounted a vane roller, 29m) Oval cam tracks are provided atthe ends oithe stator M held or heard 418/8 2351 chamber for engagingthe vane rollers ()ne or more 260-262 continuous spring hands arecontained within the rotor and produce on the vanes an outwardly biasing[56] References (nod force which urges the vane rollers into continuousUNITED STATES PA'll-IN'I'S contact with the cam tracks. The cant tracksare so 135 311 mm H 4 x 3 g symmeetrieally sized and positioned withrespect to 58,664 1/1875 Adams. 4lH/2h4 the stator chamber that with thevane rollers thus LI N l/l M rri t t t t Mi /335 maintained in contactwith the cam tracks, the vane l 4/1)24 Hlmfik":Enuhfllllmcr W tips aremaintained in clearance sealing engagement l 538.(l 5/1925 Wingqulst l v4lK/Zh3 with Wu Hf he Hmml- Chumhcl. 2,147,)4 Z/lll) [ills v i t i v v H418/258 2,672,282 3/1954 Novas 4, 418/152 28 Claims, 15 Drawing Figures1/ 1-. O l 0 4y- I 1 1 i J! l 0 O 5 Y/ Z! I i (Q) U x! 2 O O QLV ' 11/ Ol 1 1/ .f/

PATENTEUSEP ems R 3,904,327

PATENTEBSEP 9297s 3, 904, 327' SHEET u (If 5 ROTARY COMPRESSOR-EXPANDERHAVING SPRING BIASED VANES The present application is acontinuation-in-part of application Ser. No. 197,3l2 filed on Nov. I0,1971, and now abandoned.

A rotary unitary compressor-expander of the type disclosed herein isshown in U.S. Pat. No. 3,686,893. However, utilization in areas such asautomobile air conditioning requires that the cost of manufacture beminimized while assuring a reasonably long and trouble-free servicelife. In addition, the various design parameters involved requireengineering trade-offs not easily satisfied by methods utilizedheretofore. For example, the requirement of maintaining a seal betweenthe vane tip and stator surface is somewhat inconsistent with therequirement of minimum vane tip wear.

It is therefore, an object of this invention to achieve a rotary unitarycompressor-expander utilizing materials and methods of manufacture whichprovide an inexpensive unit having a long useful life. It is a morespecific object to provide a unit in which vane tip wear is minimized.It is a still more specific object of this invention to provide a rotaryunitary compressor-expander wherein the vane tips are maintained inclearance" sealing engagement with the stator chamber by the cooperativeaction between the outwardly biasing force of one or more spring bandsacting against the vanes and the positive retractive action of camtracks disposed to control radial vane travel. In this regard it is anobject to provide a unit with greatly enhanced efficiency by eliminatingsliding friction between the vane tips and stator wall.

It is a related object of this invention to provide a rotary unitarycompressor-expander in which critical to]- erances are achievedutilizing efficient and inexpensive methods of construction. In thisregard it is an object to provide a composite vane in which thevane-tip-tovane-pin spacing is achieved by relative adjustment of thecomponent parts before their joinder. It is a more specific object toprovide a method of vane assembly that achieves both accuracy andeconomy.

Other objects and advantages will become apparent from the attacheddetailed description and upon reference to the drawings in which:

FIG. 1 is an exploded view drawn in perspective of a preferredembodiment of the invention showing its major components.

FIG. 2 is a sectional front view of the compressorexpander with endplate and cam plate removed but showing the position of the cam track.

FIG. 3 is a fragmentary section taken generally along the line 33 inFIG. 2 but including the cam plate and end plate, showing therelationship between the vane, its roller, and the cam tracks.

FIG. 4, is a front view ofa single vane illustrating the preferred meansof vane pin attachment, and also illustrating a secondary springyelement.

FIG. 5 is fragmentary section along the line 5-5 of FIG. 4, showing thedove-tailing of the vane pin assembly into the vane.

FIG. 6 is a fragmentary section along the line 6-6 of FIG. 4,illustrating the secondary springy element.

FIG. 7 is a perspective view of a portion of a single vane illustratingan alternative means of attachment of the vane pin to the vane.

FIG. 8 is a fragmentary section taken along the line 88 in FIG. 7,showing a single vane pin.

FIG. 9 is a fragmentary front view of a portion of a single vane,illustrating still another method of vane pin attachment.

FIG. 10 is a fragmentary front view of the rotor, illustrating the vaneslots and the vane lubrication slots.

FIG. 11 is a fragmentary front view of the rotor illustrating vane slotinserts.

FIG. 12 is a front view of a single vane illustrating means forachieving a gas bearing.

FIG. 13 is a section along the line 13I3 of FIG. 12 showing the internalvane channels and also illustrating the vane within its slot.

FIG. 14 is a fragmentary view of an expansible spring band.

FIG. 15 is a front view of a stator with a graphitic inner liner.

While the invention will be described in connection with certainpreferred embodiments, it should be understood that I do not intend tobe limited to the particular embodiments shown but intend, on thecontrary, to cover the various alternative and equivalent constructionsincluded within the spirit and scope of the appended claims.

Turning now to the drawings and, particularly, to FIGS. 1 and 2, thereare illustrated the major components of rotary unitarycompressor-expander 20. The unit has a hollow stator member 21 having acentral opening 22 defined by wall 23 which is of oval, that iselliptical or near elliptical, cross-section. Mounted at either open endof the stator chamber are cam plates 24 and 25 having inner faces 26 and27, respectively, partially enclosing the stator chamber. Cam plates 24and 25 contain cam tracks 28 and 29, respectively which face radiallyinward. These cam tracks are of oval shape and geometricallysynchronized to the shape of stator surface 23; the relationship betweenthe two will be more fully discussed below. Enclosing ei ther end of thechamber are end plates 30 and 31 which carry aligned main bearings 32and 33. Snugly fitted between the cam plates is rotor 34 having acylindrical outer surface 37 and stub shafts 3S and 36, which engage themain bearings in the end plates. The rotor has machined in it equallyspaced radially extending slots 38 which extend the full length of therotor. It should be noted that in certain applications it may provedesirable to provide vane slots which are slightly inclined from theradial; thus references herein to radial vane slots should be read toinclude near radial orientation. The slots are occupied by vanes 39. Ateither end of rotor 34 are hollowed-out annular cavities. Cavity 40 isillustrated in FIG. 1, with the corresponding cavity 41 being a mirrorimage. Rotatably mounted on each vane at its flat base portion arealigned vane rollers 42 and 43. It is seen that each vane containsspring band notches or recesses 44 and 45. Spring bands 46 and 47 arepositioned in the hollowed-out portions 40 and 41 of the rotor to ridewithin the spring band notches 44 and 45 of all vanes 39. Theinterrelationship of these elements is shown in FIG. 2. Note that FIG. 2shows inlet and outlet ports 48 and 49 as well as heat exchanger ports50 and 51. The construction of and purpose for these ports, as well asthe utilization of the rotary unitary compressor-expander inrefrigeration, is adequately taught in prior US. Pat. No. 3,686,893therefore, these matters will be dealt with only generally herein.

The function of a rotary unitary compressorexpander, when used inrefrigeration, is to accept the fluid to be cooled, compress that fluidin the compression half of the unit, remove the heat of compression inan intercooler and expand the fluid in the expansion half of the unitbefore discharging it. HO. 2 illustrates a plurality of individualchambers in which, through rotation of the rotor, the fluid iscompressed and expanded. These chambers are defined between any twoadjacent vanes 39, rotor surface 37, stator surface 23, and cam platesurfaces 26 and 27. It is seen that to positively define theseindividual chambers, each vane 39 must be maintained in sealingengagement with stator surface 23, as well as cam surfaces 26 and 27. Inaccordance with the invention this is accomplished, while preventing anyappreciable wear on the tips of the vanes, by the cooperative action ofcam tracks 28 and 29, the plurality of vanes 39 with their vane rollers42 and 43 and spring bands 46 and 47. The cam tracks 28 and 29 are soarranged that with all vane rollers 42 and 43 maintained in contact withthose cam tracks, the tips of all vanes are maintained in a positiverelation with stator wall 23, with the cam tracks setting the limit ofvane travel and serving to positively retract the vanes. When the vaneis being extended from its slot, the cam tracks limit the extent ofradial travel while during other portions of the cycle the cam trackspositively retract the vane causing it to slide back into its slot. Itshould be noted that due to the varying angle of presentation of thevane tip to the chamber wall and non-radial (with respect to the rotor)contact of the vane roller with the cam track during parts of the cycle(see FIG. 2), the shape of the cam track does not exactly correspond tothe shape of the chamber wall. The term oval" is a general one intendedto take into account such departures from true elliptical shape.

An outwardly biasing force is maintained on the vanes by the springbands 46 and 47, pressing outwardly against the vanes in their recesses44 and 45. Thus, while the cam tracks positively limit vane travel andretract the vanes, the spring bands force the vanes outwardly causingthe vane rollers to maintain continuous contact with their respectivecam tracks. The advantages attendant to this outwardly biasing forcegenerated by the spring band are thereby achieved without theaccompanying disadvantage of vane wear which would ultimately defeat thesystem. That is, without the positive travel limitation and retractionprovided by the cam tracks, the spring bands would ultimately wear thevanes, by inward crowding action at the vane tips, to such an extentthat the bands could no longer exert an outwardly biasing force on thosevanes.

In short, the vane tips in the present construction are guided so closeto the chamber wall that they form an effective seal with it. yet thetips clear" the wall and do not exert pressure against it. Suchrelationship may be referred to for convenience, as clearance" sealingengagement; the cam track shape necessary for achieving this engagementmay be referred to as geometrically synchronized to the stator shape.The effectiveness of the seal obtained by clearance engagement isexplained in part by the fact that leakage about the ti of the vane ishighly throttled. Due to the high speed of rotation, which may in atypical case be on the order of L500 rpm., there is simply not time forany appreciable flow to occur. A further factor is that the differentialpressure on opposite sides of a given vane is in cremental," that isstage to stage, rather than total." There also develops a viscous sheerof the clearance gas (fluid between the vane tip and stator wall) whichtends to create a non-flowing boundary layer, a mechanism sometimesreferred to as visco sealing.

HO. 3 further illustrates the cooperative action between a vane, itsvane roller and the cam track, spring band and stator surface. There isseen spring band 46 riding within its recess 44 and biasing vane 39outwardly, the biasing force illustrated by the arrow. it is seen thatthis force causes vane roller 42 to contact cam track 28. Under theseconditions, it is seen that the tip of vane 39 is maintained inclearance" sealing en gagement with stator surface 23. The seal betweenthe edge of vane 39 and cam surface 26 is also illustrated.

The structure described above has been found to eliminate the vane tipwear, a major cause of failure in vane-type compressors and expanders,and in addition to greatly improve the mechanical efficiency of theunit. Both of these results derive from the fact that there is no actualcontact between the vane tip and the stator surface thus eliminatingmechanical friction at the vane tip. in addition, the reduction of dragon the vane tip reduces the cocking moment of the vane in its slotthereby reducing vane to vane slot friction. We have found, both throughtesting of actual devices and through computer predictions, thatutilization of the teachings of our invention can be expected to reducefriction by to over prior art devices.

It is apparent from the foregoing, that the relationship between the camtracks, stator surface, vane rollers, and vane tips is extremelycritical. This situation is further complicated by the fact that theserotary unitary compressor-expanders are intended for mass procluction,wherein parts should be interchangeable with a minimum of hand fitting.Manufacturing processes (e.g., numerically controlled machining) areavailable for accurately forming the oval surfaces of the stator chamberand cam tracks. Although these processes could also be applied to thevanes, this would make the completed assembly prohibitively expensive.in addition, it would impose the requirement that the vane beconstructed of a material such as steel or aluminum which has goodmachinability properties.

In the preferred embodiment of our rotary unitary compressor expander,we prefer to use a composite vane illustrated in FIGS. 4, 5 and 6. FIG.4 shows a composite van 39 made up of vane body 60 and two vane rollerassemblies 61 and 62. In this arrangement, vane body 60 is composed oflight, durable plastic material with low thermal conductivity, forexample Du- Pont Vespel SP2l. This allows the vane body to be massproduced using fairly liberal tolerances and thereby providing a vanewhose major structure is light in weight, has good frictional andthermal properties, is unaffected by the moisture in the fluid beingcooled, and is easily and inexpensively fabricated. Each vane rollerassembly 61 or 62 is preferably formed on a base 63 or 64 which isessentially a steel bracket. This bracket is drilled to snugly accept anattachment pin 65 or 66 on which vane pin 67 or 68 is tightly pressed,thereby joining the vane pin to its bracket. In the preferredembodiment, the vane pins 67 and 68 which serve as stubshafts for therollers, are of metal or other durable material machined and hardened toact as inner races for bearings 69 and 70. The outer race of eachbearing is snugly pressed into vane roller 42 or 43,

and the bearings have a close fit, so that when the bearing is assembledon its inner race, the roller is rotatably mounted free of play on itsvane bracket. In addition, each vane pin 67 or 68 is provided withgroove 71 or 72 which helps to retard the flow of lubricant away fromthe vane roller. It should be noted at this point that while the vaneroller arrangement described above provides several desirable features,if economy is the major consideration the vane rollers can be replacedby cam followers, properly contoured and fixed to the vane stub shaftsthereby eliminating both the vane rollers and their bearings.

As described above, the relationship between the vane roller and vanetip is an extremely critical one. I have found that in order to provideextended life in a vane with L936 inch spacing between the vane pincenter and the vane tip, the preferable tolerance is +0.0000 -0.0005inches. The composite vane described above provides an extremelypractical means of maintaining this critical tolerance while utilizingcomponents manufactured to liberal tolerances. This is achieved bydesigning the vane body and vane pin assemblies such that their relativeposition is adjustable prior to joinder, and permanently joining thesecomponents while they are held in an assembly fixture or jig. FIG. 5illustrates the means by which the vane body is joined to the vane pinassembly. It is seen that the vane body 60 dovetails into the vane pinassembly bracket 64. In practice, cement is applied to the matingportions of vane pin brackets 63 and 64 and vane body 60. They aredove-tailed and placed in an assembly fixture diagramaticallyillustrated at F in FIG. 4. With the rollers bottomed on surfaces Fl,the vane body 60 is extended on the fixture to engage the surface F2,thereby establishing a fitted position. If desired, the fixture endwalls F3, F4 may be set at a reference spacing for gauging purposes.With the parts held in extended position, holes are drilled through thebrackets 63 and 64 and the vane body 60, and pins 73 are pressed snuglyinto place. The end result is a relatively light and inexpensivecomposite vane, wherein the critical dimension is maintained from vaneto vane throughout an entire production run and which insures a closerunning fit between each vane and the wall of the chamber.

An additional feature which can be incorporated into composite vane 39is illustrated in FIGS. 4 and 6. It has been found that in rotarycompressor-expanders utilizing ovals in which the ratio between themajor and minor axes is relatively large, there may arise condi tionswherein additional vane biasing range is required to supplement therange of the spring band. To this end, the vanes can be provided withsecondary springy element 74 illustrated in spring band recess 45 onFIG. 4. This springy element is preferably made of spring steel andsecured to the vane by press pins 75. Its function is illustrated inFIG. 6 which shows a vane 39 with attached secondary springy element 74.The spring band 47 is shown in engagement with this springy secondaryelement. In the normal condition, the secondary springy element assumesthe position shown by the dashed lines. This is the condition whereinthe spring band 47 has sufficient range to cause the vane rollers tocontact the cam track as described above. However, in conditions whenthe range of the spring band is insufficient, the secondary springyelement expands as shown in the solid lines to provide additionaltakeup. It should be noted that this function could also be accomplishedby a rubbery secondary element attached to or dove-tailed into the vanein the spring band recesses 44 and 45.

FIGS. 7 and 8 show an alternative composite vane constructiondistinguished by extreme simplicity. Here a composite vane 39a has avane body 8] constructed substantially as described above. A vane pinassembly 82 (FIG. 8) is formed from a length of steel rod having aportion of its surface 83 machined and hardened as described above toact as the inner race for the vane roller bearing. In addition,lubrication retaining groove 84 is also provided. A slot 86 foraccepting the base of vane body 81 is formed in the vane pin as shown.Referring back to FIG. 7, the method of engagement be-- tween the vanepin assembly 82 and the vane body 81 is illustrated. In a manner similarto that described above, the relative position between these elements isadjusted in an assembly fixture before holes are drilled through thevane pin assembly and the vane body and press pin 87 are inserted. Inaddition, retainer is positioned as shown, in order to prevent outwardmove ment of the spring bands 46 and 47. In addition to providing theadvantages of the composite vane described above, this method alsoprovides a steel surface for coacting with the spring band thereby tominimize wear.

One further embodiment of vane construction is illustrated withreference to FIG. 9. There a portion of a composite vane 39b is shownwhose major structural element is a substantially rectangular vane body90. Vane pin assembly 91 is attached to this vane body via bracket 92which is positioned and pinned with pins 93. Attached to bracket 92 isoffset member 94 to which vane pin 95 is attached as shown. Vane roller96 and its bearing 97 are mounted on the vane pin, the roller 96 beingof large diameter such that when assembled as illustrated, the surfaceof the roller and the vane tip are in alignment and will simultaneouslycontact stator surface 23b as illustrated. This results in a rotaryunitary compressor-expander wherein the separate cam tracks areeliminated. As extension of the stator chamber acts as the cam track,thus eliminating the need for separate cam plates. It is seen that aspace is provided between the offset member 94 and the edge of the vane.This is to allow insertion in the stator chamber of a sealing fence 98to maintain sealing engagement with the edges of the vanes. Offsetmember 94 allows full vane travel without interferring with this sealingfence. This embodiment also illustrates use of an extension 99 on vanepin 95. This extension is provided to coact with the spring band sincethe vane illustrated here is not provided with spring band recesses. Thespring band is thus placed outboard of the rotor as illustrated at 46beliminating the need to form hollows in the rotor to ac comodate thebands. It should be noted that although this outboard spring band hasonly been illustrated with reference to this particular embodiment, itis a feature which can be incorporated into any of the previousembodiments.

In addition to eliminating vane tip wear and improving mechanicalefficiency, a further desirable feature in providing a long life unit isproper lubrication. Main rotor bearings 32 and 33 are lubricated in thenormal manner. Referring briefly to FIG. 3, the means for lubricatingthe vane rollers is illustrated. There is shown a portion of acontinuous oval slot 54 similar in shape to the cam track 28 cut in endplate 30. In this slot is disposed a lubrication retaining wick 53. Thiswick maintains a source of lubricant for the vane roller bearings andalso for the vane roller itself. In addition, the function oflubrication retaining grooves 71 and 72 in the vane pins in restrainingthe flow of lubricant away from the vane rollers has been described.Lubrication retaining fence 52 further helps maintain the lubricant asnecessary in this area.

Referring now to FIG. 10 the means for lubricating the vanes and vaneslots is shown. A fragment of rotor 34a with its numerous vane slots 38ais shown in end view. It is seen that intersecting each vane slot arelubrication slots 100. Inserted in these lubrication slots arelubrication retaining wicks 101 which maintain a source of lubricant forthe vanes and vane slots.

An alternative means for reducing friction between the vane and its slotis shown in FIG. 11. There a frag ment of rotor 34b is again shown inend view. This embodiment is similar to FIG. 10 except that thelubrication slots are removed and the vane slots 38b are enlarged toaccept inserts 105. These inserts are bonded to their enlarged slotsthereby to provide a composite vane slot. The inserts are made of amaterial with a low coefficient of friction such as DuPont Vespel SP2Ithereby providing a freely sliding assembly. In addition a gas bearingeffect can be achieved by modifying the vane slot inserts as shown byinsert 106 in FIG. 11 which is cut away to illustrate one of a pluralityof internal channels 107. These internal channels communicate to thevane slot through ports 108. In form they are similar to the vanechannels illustrated in FIGS. 12 and 13 (to be described below) howeverthey difi'er in that the channels communicate through ports 109 with thecompressor-expander chambers. It is seen that a small portion of thepressurized fluid in the individual chamber is forced through port 109into channel 107 and through ports 108 into the vane slot creating acushion of air between the vane and its slot. As the inserts are bondedto the rotor the channels can be formed of grooves on the side of insert106 which will mate with the rotor. It is obvious that using thesemeans, channels cannot be provided in portions of the insertcorresponding to the hollowed out portions of the rotor, therefore it ispreferable to utilize these means with rotors having no internal springband cavities.

An extremely durable unit is achieved by utilizing inserts made ofsteel, having internal rows of aligned rol' ler bearings. The rollersare arranged so that their axes are perpendicular to the direction ofvane travel, and so that the roller surfaces barely project into thevane slots.

A vane to vane-slot gas bearing is provided by the means illustrated inFIGS. 12 and 13. There is shown a modified vane 39c adapted to be usedin a unit wherein the spring bands are positioned outboard of the rotorthereby to allow use of a rotor without hollows to accomodate the springband. It should be noted that the vane pins are shown diagrammaticallyas any of the above described means of attachment can be used. Asillustrated, the vane is provided with numerous internal channels 110,communicating with the vane surface via numerous ports 11] and 112.These channels and ports are disposed to allow passage of the fluidbeing cooled. FIG. 13 illustrates a vane 39c inserted in its vane slot380 in the rotor. It is seen that the position of the vane in its slotcauses some of the ports 112 to be enclosed within the vane slot whileother of the ports 111 are above the rotor surface 370. Thus a portionof the fluid within the individual compressor or expander cavities isforced through ports 11], through channels and through ports 112creating a cushion between the vane and its slot thus providing a gasbearing effect. It should be noted that in the illustrated embodiment aset of channels is provided on either side of the vane; but the passageon either side of the vane are not connected thereby preventing pressureleakage between adjacent chambers.

Although the function of the spring band has been described above, theactual structure has not been dealt with in detail. In its simplestembodiment, each band is a continuous loop of spring steel. The loop isso sized that when it is positioned in the spring band recesses of itsassociated vanes, as illustrated in FIG. 2, (or against its vane pinextension if a spring band is used which is outboard of the rotor) itassumes an oval shape similar to the shape of the stator surface and camtracks and forces all vane rollers into contact with the cam tracks.Rotation of the rotor causes the band to generally rotate with the rotorand its vanes while maintaining its oval profile, thereby maintaining abiasing force on all of the vanes. In a preferred embodiment, each bandis composed of a laminate consisting of several loops of band materialnested together to form a composite band. Such arrangement allows theuse of relatively thin, individual layers which will be subject tocomparatively lower stresses while still providing the necessary totalbiasing force. In addition, we have found it useful to provide a tefloncoating on the spring bands to minimize wear on the band and itsassociated slots. When using multiple nested bands, this teflon coatingallows the layers to slip on each other assuring equalized distributionof force to the vanes.

One further embodiment of spring band construction should be discussed.As noted above, when using rotary unitary compressor-expanders withelongted ovals, there may arise conditions wherein the biasing forcegenerated by the spring band 46 and 47 must be supplemented by meanssuch as the secondary springy element 74 of FIG. 6. The need for thesesecondary springy elements may be eliminated by providing a spring bandwhich is truly expansible, a fragment of which is illustrated in FIG.14. To that end, a spring band is used which is formed from a singlemultiwrapped band 46c of relatively thin band material with free ends46d, and 46e and outwardly sprung. Such band, teflon coated, is free toexpand and contract providing a continuous biasing force to all vaneseven in greatly elongated oval configuration and with greater availabletakeup, if necessary, for wear.

While the preferred form of the invention contemplates use of acontinuous spring band, it will be apparent to one skilled in the artthat the invention, in certain of its aspects, it not limited to use ofthe spring band and that, if desired, individual springs associated witheach vane may be used to bias such vanes outwardly with respect to therotor. In this case, just as in those described above, the vanes do notpress against the inner wall of the chamber but they are, indeed,prevented from doing so by the engagement of the vane rollers with theirrespective cam tracks.

In the preferred embodiment of the rotary unitary compressor-expanderdescribed above, it was stated that the stator surface and cam tracksmust be machined with great accuracy. In addition, means formanufacturing identical vanes are disclosed. We have found that theseaccurately manufactured vanes can be used in a modified construction toallow more liberal tolerances to be used in forming the stator surface.It should be appreciated that the distance between the cam track andstator surface as measured along any radial line extending from therotor center is fixed. This distance is a function ofvane-pin-to-vane-tip spacing. In accordance with this aspect of theinvention, the cam tracks are accurately machined as described above andthe required surface finish provided. However, the stator chamber isformed using more liberal tolerances with minimal attention given tosurface finish. The main requirement in forming the stator chamber isthat the opening be slightly larger than the design size as dicated bythe cam tracks and vanes. The curved wall of the chamber is then coatedwith a layer of graphite material uniformly distributed in a binderwhich forms a stator chamber which is slightly smaller than the designsize. A usable graphite material is a carbon graphite mixture combinedwith an epoxy binder. When the unit is assembled, the spring bands willbias the vane tips into contact with the chamber liner which will, inturn, prevent the vane rollers from contacting their cam tracks. Therotor is then rotated during a run-in" period which results in the vaneswearing away the comparatively softer graphitic surface until the vanerollers come into contact their cam tracks. As all the vanes haveidentical vane pin to vane tip spacing, it is seen that the rotorsurface thus formed yields the required clearance sealing engagementbetween all vane tips and the rotor surface through all positions ofrotor rotation. The result is a graphitic liner illustrated as 102 inFIG. formed within the stator chamber. The liner material may be cast inplace, if desired, followed by run-in."

The graphitic liner discussed above in addition to reducing theprecision machining required provides an additional benefit. It has animportant effect in maintaining the efficiency of the rotary unitarycompressor expander by reason of thermal management. It will beappreciated that the fluid being cooled undergoes sig nificant changesin temperature during a cycle. In gen eral direct heat transfer throughthe device should be minimized so that the heat generated in thecompression process is not conducted via the machine elements andtransferred back to the cooled fluid resulting from the expansionprocess. Stated simply, it is important to prevent the hot (orcompression) side of the unit from transferring heat to the cold (orexpansion) side so that the expansion process can be performedadiabatically. The graphitic liner 102 (FIG. 15) has an important rolein preventing this unwanted heat transfer as it has low coefficient ofthermal conductivity. This liner thereby retards heat transfer to thestator housing 21a which acts as a conductive path. It should beappreciated that what is required for efficient thermal management is aneffective thermal block between the compression side and the expansionside of the device. This can be achieved in addition to the graphiticliner described above by thermal blockages between the two halves of thestator such as the slots illustrated as 88 and 89 on FIGS. 1 and 2 whichdecrease the area for heat conduc tion. Also, as described above theindividual vanes are made of a plastic material with a low coefficientof thermal conductivity thereby yielding an efficient thermal blockbetween adjacent cavities and preventing them from transferringappreciable heat during a rotational cycle. In addition, the surface ofthe rotor may be coated with insulating material between the vanes.

Throughout this description the material to be refrigerated has beenreferred to interchangeably as fluid or air. While air is the preferredmedium, it will be understood that the device disclosed is applicable tocompressible fluids in general.

We claim as our invention:

1. A rotary unitary compressor-expander for use in a refrigerationdevice comprising in combination, a stator including a hollow memberenclosed by respective end members defining a chamber having a wall ofoval cross section, a rotor rotatably mounted in axial position in thestator chamber, the rotor having a plurality of equally spaced radialvane slots, a plurality of vanes snugly slideable in the respective vaneslots, each of said vanes having a base portion and having a radiallypresented vane tip, the base portion having aligned axially extendingstubshafts fitted with cam followers, a continuous inwardly facing camtrack at each end of the stator chamber for engaging the respective camfollowers on each of the vanes, spring band biasing means operativelyassociated with the vanes for urging the vanes radially outwardly tokeep the cam followers thereon biased against the cam tracks, said camtracks being of oval configuration geometrically synchronized to theoval wall of the chamber so that the tips of said vanes are maintainedin continuous clearance sealing engagement with the wall, the cam tracksserving to resist the biasing force and to positively retract the vanesinwardly during portion of the rotational cycle thereby to avoidcrowding, with resultant wear and friction at the tips of the vanes.

2. A rotary unitary compressor-expander for use in a refrigerationdevice comprising in combination, 8 Sta tor including a hollow memberenclosed by respective end members defining a chamber having a wall ofoval cross section, a rotor rotatably mounted in axial position in thestator chamber, the rotor having a plurality of equally spaced radialvane slots, a plurality of vanes snugly slideable in the respective vaneslots, each of said vanes having a flat base portion and having aradially presented vane tip, the base portion having aligned axiallyextending stubshafts, closely fitted rollers on the stubshafts, acontinuous inwardly facing cam track in each of the end members forengaging the respective rollers on each of the vanes, continuous springband means arranged to press outwardly on the vanes to bias the vanesand to keep the rollers thereon biased radially outwardly against thecam tracks, said tracks being of oval configuration and so symmetricallysized and positioned with respect to the oval wall of the chamber thatthe tips of said vanes are maintained in continuous clearance sealingengagement with such wall, the cam tracks serving to resist the biasingforce and to posi tively retract the vanes inwardly during portions ofthe rotational cycle thereby to avoid crowding with resultant wear andfriction at the tips of the vanes.

3. A rotary unitary compressor-expander for use in a refrigerationdevice comprising in combination, a stator including a hollow memberenclosed by respective end members defining a chamber having a wall ofoval cross section, a hollow rotor rotatably mounted in axial positionin the stator chamber, the rotor having a plurality of equally spacedradial vane slots, a plurality of vanes snugly slideable in therespective vane slots, each of said vanes having a flat base portionwith spaced notches formed therein and having a radially presented vanetip, the base portion having aligned axially extending stubshafts.closely fitted rollers on the stubshafts, a continuous inwardly facingcam track in each of the end members for engaging the respective rollerson each of the vanes, a pair of continuous spring bands axially spacedin the hollow of the rotor and arranged to press outwardly in thenotches of the vanes to keep the rollers thereon biased radiallyoutwards against the cam tracks, said cam tracks being of ovalconfiguration and so symmetrically sized and positioned with respect tothe oval wall of chamber that the tips of said vanes are maintained incontinuous clearance sealing engagement with the wall of the chamberwhile prevented from contacting such wall, thereby to minimize friction,reducing wear and increasing efficiency.

4. A rotary unitary compressor-expander for use in a refrigerationdevice comprising in combination, a stator including a hollow memberenclosed by respective end members defining a chamber having a wall ofoval cross section, a rotor rotatably mounted in axial position in thestator chamber, the rotor having a plurality of equally spaced radialvane slots, a plurality of vanes snugly slideable in the respective vaneslots, each of said vanes having a flat base portion and having aradially presented vane tip, the base portion having aligned axiallyextending stubshafts, closely fitted rollers on the stubshafts, acontinuous inwardly facing cam track at each end of the stator chamberfor engaging the respective rollers on each of the vanes, meansincluding a re silient spring band arranged to press outwardly on thevanes to bias the vanes and to keep the rollers thereon biased radiallyoutwardly against the cam tracks, said cam tracks being of ovalconfiguration and so symmetrically sized and positioned with respect tothe oval chamber that the tips of said vanes are maintained incontinuous clearance sealing engagement with the wall, the cam tracksserving to resist the biasing force and to positively retract the vanesinwardly during portions of the rotational cycle thereby to minimizewear and friction at the tips of the vanes, the band being of laminatedconstruction formed of a thin helically wound strip with unsecured endsand outwardly sprung to take up radial movement of the vane.

5. A rotary unitary compressorexpander for use in a refrigeration devicecomprising in combination, a stator including a hollow member enclosedby respective end members defining a chamber having a wall of oval crosssection, a rotor rotatably mounted in axial position in the statorchamber, the rotor having a plurality of equally spaced radial vaneslots, a plurality of vanes snugly slideable in the respective vaneslots, each of said vanes having a base portion and having a radiallypresented vane tip, the base portion having aligned axially extendingstubshafts, closely fitted rollers on the stubshafts, a continuousinwardly facing cam track at each end of the stator chamber for engagingthe respective rollers on each of the vanes, spring band biasing meansoperatively associated with the vanes for urging the vanes radiallyoutwardly to keep the rollers thereon biased against the cam tracks,said cam tracks being of oval configuration and geometricallysynchronized to the oval wall of the chamber so that the tips of saidvanes are maintained in continuous clearance sealing engagement withsuch wall, the cam tracks serving to resist the biasing force and topositively retract the vanes inwardly during portions of the rotationalcycle thereby to avoid crowding, with resultant wear and friction at thetips of the vanes.

6. The combination as claimed in claim 5 in which each vane is ofcomposite construction including a flat vane body of light plastichaving brackets thereon for mounting the aligned stubshafts, thebrackets being radially moveable on the vane body into fitted positionof precise dimension between the stubshafts and the tip of the vanethereby to insure a close running fit between the tips of all the vanesand the oval wall of the cham her, the brackets having means for fixingthe same in fitted positions.

7. The combination as claimed in claim 6 in which the biasing meanscomprises a pair of continuous spring bands, and the stubshafts includerespective stubshaft extensions for coacting with the spring bandswhereby said bands are positioned outboard of the rotor.

8. The combination as claimed in claim 1 in which each vane is ofcomposite construction including a flat vane body of light plastic andincluding brackets mounting the stubshafts, said stubshafts being ofdurable material and extending in axial alignment from the brackets, thebrackets having grooves mating with the respective lateral edges of thevane body to provide relative radial sliding movement and with thebrackets being pinned to the vane body in a fitted position in whichthere exists a precise radial dimension between the stubshafts and thetip of the vane.

9. The combination as claimed in claim 8 in which the biasing meanscomprises a pair of continuous spring bands, and the stubshafts includerespective stubshaft extensions for coacting with the spring bandswhereby said bands are positioned outboard of the rotor.

10. The combination as claimed in claim 5 in which the portion of eachvane slot engaged with the vane includes insert members fixed to therotor for providing a smooth surface to contact the vanes therebyreducing vane to vane slot friction.

11. The combination as claimed in claim 10 in which the insert membersinclude a pattern of radially extending channels terminating in apattern of ports at the engaged surfaces and in which means are providedfor supplying to the channels a portion of the air compressed in thechambers thereby to establish a film or air at the engaged surfaces forlubricating the same.

12. The combination as claimed in claim 5 in which the biasing meansincludes a pair of continuous spring bands arranged to press outwardlyon the vanes.

13. The combination as claimed in claim 12 in which each vane isprovided with a resilient cushion mounted thereon at the region ofengagement between the vane and the band to thereby increase the rangeof resilient follow up action of the vane.

14. The combination as claimed in claim 12 in which each vane is ofcomposite construction including a flat vane body of light plastic thestubshafts being of elongated construction including a slotted extensionpor tion mating with the base portion of the vane body, the extensionportion being pinned to the vane body in a fitted position in whichthere exists a precise radial dimension between the stubshafts and thetip of the vane, the extension portions of the stubshafts engaging thespring bands thereby to minimize wear.

15. The combination as claimed in claim 14 in which the portion of eachvane engaged with the vane slot includes a plurality of radiallyextending internal channels terminating in a pattern of ports at theengaged surfaces and in which means are provided for continuouslysupplying to the channels a portion of the air compressed in thechambers thereby to establish a film of air at the engaged surfaces forlubricating the same.

16. The combination as claimed in claim 15 in which each vane includes aplurality of radially extending channels including a pattern of ports inboth the portion of the vane engaged with the vane slot and the portionof the vane extending into the chamber so that a portion of aircompressed in the chamber flows through the channel to the vane slotthereby to establish a film of air at the engaged surfaces forlubricating the same.

17. The combination as claimed in claim 14 in which rotation of therotor in a given direction defines a compression half and an expansionhalf of the compressorexpander and the stator includes thermal blockingmeans interposed between the halves of the stator to retard heattransfer through the stator between the compression and expansion sidesto more nearly approach the efficiency of adiabatic expansion on theexpansion side.

18. The combination as claimed in claim 17 in which the vanes are formedof a plastic material having thermal insulating properties.

19. The combination as claimed in claim 17 in which the thermal blockingmeans comprises slots formed in the exterior of the stator to decreasethe area for heat transfer between said halves through the stator.

20. The combination as claimed in claim 1 in which the stubshafts areformed separately from the vane which carries them and in which meansare provided for precisely locating the radial position of thestubshafts with respect to the tip of the vane thereby to insure a closerunning fit between the tips of all the vanes and the oval wall of thechamber.

21. The combination as claimed in claim 20 in which the biasing meanscomprises a pair of continuous spring bands. and the stubshafts includerespective stubshaft extensions for coacting with the spring bandswhereby said bands are positioned outboard of the rotor.

22. The combination as claimed in claim 20 further including alubrication retaining force extending inwardly from each cam tracktoward the respective stubshafts and interposed between the vanebrackets and the vane rollers.

23. The combination as claimed in claim 4 in which the cam trackscomprise an extension of the oval wall of the stator chamber.

24. The combination as claimed in claim 23 in which stationary fencesare provided at the ends of the stator between the vanes and therespective rollers thereon for sealing engagement with the lateral edgesof the vanes.

25. The combination claimed in claim 20 in which the stator chamber isof enlarged size to produce a gap between the oval wall and the vanetips when the rollers are biased against the cam tracks, the wall ofchamber being coated with a layer of graphitic material uniformlydistributed in a binder to close said gap, said graphite material beingsofter than the material comprising the tips of the vanes so as toundergo intentional wear during run-in and until the rollers are freelyseated on the cam tracks thereby to provide the clearance sealingengagement between the tips of the vanes and the coated wall.

26. The combination as claimed in claim 25 in which the inner wall ofthe stator is coated with a layer of material having thermal insulatingas well as lubricating properties thereby to further enhance theadiabatic nature of the expansion.

27. The combination as claimed in claim 26 in which the layer ofinsulating and lubricating material consists of graphitic materialuniformly distributed in an insulating binder.

28. The combination as claimed in claim 27 in which the insulatingbinder is an epoxy resin.

1. A rotary unitary compressor-expander for use in a refrigerationdevice comprising in combination, a stator including a hollow memberenclosed by respective end members defining a chamber having a wall ofoval cross section, a rotor rotatably mounted in axial position in thestator chamber, the rotor having a plurality of equally spaced radialvane slots, a plurality of vanes snugly slideable in the respective vaneslots, each of said vanes having a base portion and having a radiallypresented vane tip, the base portion having aligned axially extendingstubshafts fitted with cam followers, a continuous inwardly facing camtrack at each end of the stator chamber for engaging the respective camfollowers on each of the vanes, spring band biasing means operativelyassociated with the vanes for urging the vanes radially outwardly tokeep the cam followers thereon biased against the cam tracks, said camtracks being of oval configuration geometrically synchronized to theoval wall of the chamber so that the tips of said vanes are maintainedin continuous clearance sealing engagement with the wall, the cam tracksserving to resist the biasing force and to positively retract the vanesinwardly during portion of the rotational cycle thereby to avoidcrowding, with resultant wear and friction at the tips of the vanes. 2.A rotary unitary compressor-expander for use in a refrigeration devicecomprising in combination, a stator including a hollow member enclosedby respective end members defining a chamber having a wall of oval crosssection, a rotor rotatablY mounted in axial position in the statorchamber, the rotor having a plurality of equally spaced radial vaneslots, a plurality of vanes snugly slideable in the respective vaneslots, each of said vanes having a flat base portion and having aradially presented vane tip, the base portion having aligned axiallyextending stubshafts, closely fitted rollers on the stubshafts, acontinuous inwardly facing cam track in each of the end members forengaging the respective rollers on each of the vanes, continuous springband means arranged to press outwardly on the vanes to bias the vanesand to keep the rollers thereon biased radially outwardly against thecam tracks, said tracks being of oval configuration and so symmetricallysized and positioned with respect to the oval wall of the chamber thatthe tips of said vanes are maintained in continuous clearance sealingengagement with such wall, the cam tracks serving to resist the biasingforce and to positively retract the vanes inwardly during portions ofthe rotational cycle thereby to avoid crowding with resultant wear andfriction at the tips of the vanes.
 3. A rotary unitarycompressor-expander for use in a refrigeration device comprising incombination, a stator including a hollow member enclosed by respectiveend members defining a chamber having a wall of oval cross section, ahollow rotor rotatably mounted in axial position in the stator chamber,the rotor having a plurality of equally spaced radial vane slots, aplurality of vanes snugly slideable in the respective vane slots, eachof said vanes having a flat base portion with spaced notches formedtherein and having a radially presented vane tip, the base portionhaving aligned axially extending stubshafts, closely fitted rollers onthe stubshafts, a continuous inwardly facing cam track in each of theend members for engaging the respective rollers on each of the vanes, apair of continuous spring bands axially spaced in the hollow of therotor and arranged to press outwardly in the notches of the vanes tokeep the rollers thereon biased radially outwards against the camtracks, said cam tracks being of oval configuration and so symmetricallysized and positioned with respect to the oval wall of chamber that thetips of said vanes are maintained in continuous clearance sealingengagement with the wall of the chamber while prevented from contactingsuch wall, thereby to minimize friction, reducing wear and increasingefficiency.
 4. A rotary unitary compressor-expander for use in arefrigeration device comprising in combination, a stator including ahollow member enclosed by respective end members defining a chamberhaving a wall of oval cross section, a rotor rotatably mounted in axialposition in the stator chamber, the rotor having a plurality of equallyspaced radial vane slots, a plurality of vanes snugly slideable in therespective vane slots, each of said vanes having a flat base portion andhaving a radially presented vane tip, the base portion having alignedaxially extending stubshafts, closely fitted rollers on the stubshafts,a continuous inwardly facing cam track at each end of the stator chamberfor engaging the respective rollers on each of the vanes, meansincluding a resilient spring band arranged to press outwardly on thevanes to bias the vanes and to keep the rollers thereon biased radiallyoutwardly against the cam tracks, said cam tracks being of ovalconfiguration and so symmetrically sized and positioned with respect tothe oval chamber that the tips of said vanes are maintained incontinuous clearance sealing engagement with the wall, the cam tracksserving to resist the biasing force and to positively retract the vanesinwardly during portions of the rotational cycle thereby to minimizewear and friction at the tips of the vanes, the band being of laminatedconstruction formed of a thin helically wound strip with unsecured endsand outwardly sprung to take up radial movement of the vane.
 5. A rotaryunitary compressor-expander for use in A refrigeration device comprisingin combination, a stator including a hollow member enclosed byrespective end members defining a chamber having a wall of oval crosssection, a rotor rotatably mounted in axial position in the statorchamber, the rotor having a plurality of equally spaced radial vaneslots, a plurality of vanes snugly slideable in the respective vaneslots, each of said vanes having a base portion and having a radiallypresented vane tip, the base portion having aligned axially extendingstubshafts, closely fitted rollers on the stubshafts, a continuousinwardly facing cam track at each end of the stator chamber for engagingthe respective rollers on each of the vanes, spring band biasing meansoperatively associated with the vanes for urging the vanes radiallyoutwardly to keep the rollers thereon biased against the cam tracks,said cam tracks being of oval configuration and geometricallysynchronized to the oval wall of the chamber so that the tips of saidvanes are maintained in continuous clearance sealing engagement withsuch wall, the cam tracks serving to resist the biasing force and topositively retract the vanes inwardly during portions of the rotationalcycle thereby to avoid crowding, with resultant wear and friction at thetips of the vanes.
 6. The combination as claimed in claim 5 in whicheach vane is of composite construction including a flat vane body oflight plastic having brackets thereon for mounting the alignedstubshafts, the brackets being radially moveable on the vane body intofitted position of precise dimension between the stubshafts and the tipof the vane thereby to insure a close running fit between the tips ofall the vanes and the oval wall of the chamber, the brackets havingmeans for fixing the same in fitted positions.
 7. The combination asclaimed in claim 6 in which the biasing means comprises a pair ofcontinuous spring bands, and the stubshafts include respective stubshaftextensions for coacting with the spring bands whereby said bands arepositioned outboard of the rotor.
 8. The combination as claimed in claim1 in which each vane is of composite construction including a flat vanebody of light plastic and including brackets mounting the stubshafts,said stubshafts being of durable material and extending in axialalignment from the brackets, the brackets having grooves mating with therespective lateral edges of the vane body to provide relative radialsliding movement and with the brackets being pinned to the vane body ina fitted position in which there exists a precise radial dimensionbetween the stubshafts and the tip of the vane.
 9. The combination asclaimed in claim 8 in which the biasing means comprises a pair ofcontinuous spring bands, and the stubshafts include respective stubshaftextensions for coacting with the spring bands whereby said bands arepositioned outboard of the rotor.
 10. The combination as claimed inclaim 5 in which the portion of each vane slot engaged with the vaneincludes insert members fixed to the rotor for providing a smoothsurface to contact the vanes thereby reducing vane to vane slotfriction.
 11. The combination as claimed in claim 10 in which the insertmembers include a pattern of radially extending channels terminating ina pattern of ports at the engaged surfaces and in which means areprovided for supplying to the channels a portion of the air compressedin the chambers thereby to establish a film or air at the engagedsurfaces for lubricating the same.
 12. The combination as claimed inclaim 5 in which the biasing means includes a pair of continuous springbands arranged to press outwardly on the vanes.
 13. The combination asclaimed in claim 12 in which each vane is provided with a resilientcushion mounted thereon at the region of engagement between the vane andthe band to thereby increase the range of resilient follow up action ofthe vane.
 14. The combination as claimed in claim 12 in which each vaneis of composite construction incLuding a flat vane body of light plasticthe stubshafts being of elongated construction including a slottedextension portion mating with the base portion of the vane body, theextension portion being pinned to the vane body in a fitted position inwhich there exists a precise radial dimension between the stubshafts andthe tip of the vane, the extension portions of the stubshafts engagingthe spring bands thereby to minimize wear.
 15. The combination asclaimed in claim 14 in which the portion of each vane engaged with thevane slot includes a plurality of radially extending internal channelsterminating in a pattern of ports at the engaged surfaces and in whichmeans are provided for continuously supplying to the channels a portionof the air compressed in the chambers thereby to establish a film of airat the engaged surfaces for lubricating the same.
 16. The combination asclaimed in claim 15 in which each vane includes a plurality of radiallyextending channels including a pattern of ports in both the portion ofthe vane engaged with the vane slot and the portion of the vaneextending into the chamber so that a portion of air compressed in thechamber flows through the channel to the vane slot thereby to establisha film of air at the engaged surfaces for lubricating the same.
 17. Thecombination as claimed in claim 14 in which rotation of the rotor in agiven direction defines a compression half and an expansion half of thecompressor-expander and the stator includes thermal blocking meansinterposed between the halves of the stator to retard heat transferthrough the stator between the compression and expansion sides to morenearly approach the efficiency of adiabatic expansion on the expansionside.
 18. The combination as claimed in claim 17 in which the vanes areformed of a plastic material having thermal insulating properties. 19.The combination as claimed in claim 17 in which the thermal blockingmeans comprises slots formed in the exterior of the stator to decreasethe area for heat transfer between said halves through the stator. 20.The combination as claimed in claim 1 in which the stubshafts are formedseparately from the vane which carries them and in which means areprovided for precisely locating the radial position of the stubshaftswith respect to the tip of the vane thereby to insure a close runningfit between the tips of all the vanes and the oval wall of the chamber.21. The combination as claimed in claim 20 in which the biasing meanscomprises a pair of continuous spring bands, and the stubshafts includerespective stubshaft extensions for coacting with the spring bandswhereby said bands are positioned outboard of the rotor.
 22. Thecombination as claimed in claim 20 further including a lubricationretaining force extending inwardly from each cam track toward therespective stubshafts and interposed between the vane brackets and thevane rollers.
 23. The combination as claimed in claim 4 in which the camtracks comprise an extension of the oval wall of the stator chamber. 24.The combination as claimed in claim 23 in which stationary fences areprovided at the ends of the stator between the vanes and the respectiverollers thereon for sealing engagement with the lateral edges of thevanes.
 25. The combination claimed in claim 20 in which the statorchamber is of enlarged size to produce a gap between the oval wall andthe vane tips when the rollers are biased against the cam tracks, thewall of chamber being coated with a layer of graphitic materialuniformly distributed in a binder to close said gap, said graphitematerial being softer than the material comprising the tips of the vanesso as to undergo intentional wear during run-in and until the rollersare freely seated on the cam tracks thereby to provide the clearancesealing engagement between the tips of the vanes and the coated wall.26. The combination as claimed in claim 25 in which the inner wall ofthe stator is coated with a layer of material having thermal insulatingas well as lubricating properties thereby to further enhance theadiabatic nature of the expansion.
 27. The combination as claimed inclaim 26 in which the layer of insulating and lubricating materialconsists of graphitic material uniformly distributed in an insulatingbinder.
 28. The combination as claimed in claim 27 in which theinsulating binder is an epoxy resin.